NSF-Funded Researchers Discover Evidence of Microscopic
Life at the South Pole

In a finding that may extend the known limits of life
on Earth, researchers supported by the National Science
Foundation (NSF) have discovered evidence that microbes
may be able to survive the heavy doses of ultraviolet
radiation and the extreme cold and darkness of the
South Pole.

The team's findings, published in Applied and Environmental
Microbiology, the journal of the American Society
for Microbiology, indicate that a population of active
bacteria, some of which have DNA sequences that align
closely with species in the genus Deinococcus,
exists at the South Pole in the austral summer. A
similar species lives elsewhere in Antarctica, but
the discovery of microbes at the Pole may mean that
the bacteria have become uniquely adapted to the extreme
conditions there, including a scarcity of liquid water.

A species in the genus Deinococcus was first
discovered in cans of irradiated meat in the 1950's,
and is able to withstand extreme dryness and large
doses of radiation. It is possible that the related
bacteria from the South Pole may also possess these
characteristics.

"While we expected to find some bacteria in the South
Pole snow, we were surprised that they were metabolically
active and synthesizing DNA and protein at local ambient
temperatures of -12 to -17 Celsius (10.4 to 1.4 degrees
Fahrenheit)," said Edward J. Carpenter, of the State
University of New York at Stony Brook, who headed
the research team. "Before attempting to publish the
results, we wanted to be certain that the data were
correct and were able to duplicate the observations
in a second field season during January 2000."

Antarctica was once part of a supercontinent called
Gondwanaland and drifted into its present position
only about 60 million years ago. Deinococcus,
however, is thought to be one of the earlier branches
in the bacterial tree, and is much older than Antarctica
in its present location. It is therefore unlikely
that it evolved in Antarctica.

If the team's conclusions prove true, the discovery
not only has important implications for the search
for life in other extreme environments on Earth, but
also for the possibility that life -- at least at
the microscopic level -- may exist elsewhere in the
solar system. Furthermore, the snow bacteria may possess
unique enzymes and membranes able to cope with a subzero
existence.

The team was careful to take samples at the edge of
the clean-air sector at Amundsen-Scott South Pole
Station to prevent contamination of the samples by
bacteria from human habitation. The containers of
bacteria were flown, still frozen, within 24 hours
to the Albert P. Crary Science and Engineering Center
at NSF's McMurdo Station for analysis. In examining
the snowmelt, the researchers found coccoid and rod-shaped
bacteria, some of which appeared to be dividing.

The findings by Carpenter and his colleagues, Senjie
Lin, of the University of Connecticut, and Douglas
Capone, of the University of Southern California,
also may be significant because a separate team of
NSF-supported investigators reported that ice cores
taken at Lake Vostok, deep in the Antarctic interior,
indicate the presence of microbes in what is suspected
to be a vast pool of liquid water thousands of meters
below the Antarctic ice sheet. That finding may have
similar implications for extending the known limits
of life.